Daily guide · PL · 2026-08-16
What a home battery earned in Poland this week, hour by hour
All numbers computed from the week's published auction results at publication and frozen — this article is an honest snapshot, not a page that rewrites itself. Reproduce via the API.
The pattern this week was unusually consistent. On every one of the seven days the cheapest window opened in the early afternoon, between 12:00 and 14:00, while the evening peak arrived at 19:00 or 20:00. That midday-to-evening spread is the core of home-battery arbitrage: charge when solar pushes prices down, discharge into the demand peak. The average spread across the week reached 241,77 EUR/MWh.
What stands out is how negative the charging window went on some days. On 9 August the cheap average was -2,34 EUR/MWh and on 11 August it fell to -9,20 EUR/MWh, meaning a battery was effectively paid to absorb power before selling into peaks of 261,84 and 176,58 EUR/MWh. The strongest single day was 13 August, pairing a 52,53 EUR/MWh trough with a 332,73 EUR/MWh peak for a cycle value of 2,47 EUR.
For a 10 kWh battery at 90 percent round-trip efficiency, the full week returned 15,09 EUR, which annualises to 787 EUR. The concrete takeaway: hold your discharge for the 19:00–20:00 peak, since that timing held every day.
A home battery makes money on one thing: the gap between the day's cheapest and priciest hours. Charge low, discharge across the evening peak instead of buying it, repeat daily. The size of that gap is set every afternoon at the day-ahead auction — so it's measurable, not hypothetical. Here is what one full daily cycle of a 10 kWh battery (at 90% round-trip efficiency — losses included, unlike most brochures) would have captured in PL this week.
€15.09
captured this week — one cycle per day, wholesale component, after losses
241.77
€/MWh average cheapest-2h → priciest-2h spread this week
≈€787
a year at this week's spreads — the honest run-rate, not the best-day fantasy
Day by day: the two windows that mattered
| Day | Charge (2h) | at €/MWh | Discharge (2h) | at €/MWh | Cycle value |
|---|---|---|---|---|---|
| 2026-08-09 | 12:00–14:00 | -2.34 | 19:00–21:00 | 176.58 | €1.61 |
| 2026-08-10 | 12:00–14:00 | 64.59 | 19:00–21:00 | 325.18 | €2.28 |
| 2026-08-11 | 14:00–16:00 | -9.2 | 20:00–22:00 | 261.84 | €2.45 |
| 2026-08-12 | 12:00–14:00 | 23.8 | 19:00–21:00 | 299.69 | €2.46 |
| 2026-08-13 | 13:00–15:00 | 52.53 | 19:00–21:00 | 332.73 | €2.47 |
| 2026-08-14 | 12:00–14:00 | 12.85 | 19:00–21:00 | 254.41 | €2.16 |
| 2026-08-15 | 12:00–14:00 | 0 | 20:00–22:00 | 184.17 | €1.66 |
Local time, hourly auction means. Days where charging was negative-priced mean you were paid to fill the battery.
Do it automatically
The windows move every day — automation is the whole game. One API call returns a cost-optimal schedule your inverter or energy manager can follow, and there's a full battery simulator to backtest your exact capacity, power and cycle limits against realized prices before you trust it:
curl -X POST -H "Authorization: Bearer YOUR_KEY" \
-H "Content-Type: application/json" \
-d '{"zone": "PL", "capacity_kwh": 10, "max_power_kw": 5,
"round_trip_efficiency": 0.9, "max_cycles_per_day": 1}' \
https://voltcast.com/api/v1/optimize/batteryHome Assistant users get the schedule as a sensor via the integration. And because the value depends entirely on tomorrow's spread, the P10–P90 forecast — scored publicly every day — tells you whether tomorrow is worth a deep cycle at all.
Method & citation. Prices are hourly means of published day-ahead auction results (native 15-minute periods averaged; ENTSO-E/SMARD, attributed). Wholesale-price component only — grid fees and taxes come on top and vary by supplier. Cite as "Voltcast Research, voltcast.com/guides/battery-arbitrage-pl-2026-08-16".
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